Use purl format

Fix identifier (hopefully).

Author: martincostello

.github/workflows/dependency-review.yml

@@ -24,5 +24,5 @@ jobs:
       - name: Review dependencies
         uses: actions/dependency-review-action@da24556b548a50705dd671f47852072ea4c105d9 # v4.7.1
         with:
-          allow-dependencies-licenses: 'grafana/shared-workflows/actions/get-vault-secrets'
+          allow-dependencies-licenses: 'pkg:github/grafana/shared-workflows/actions/get-vault-secrets'
           allow-licenses: 'Apache-2.0,BSD-3-Clause,MIT'